In various technological fields, and in particular in the pharmaceutical field, it is necessary to produce bulk material in the form of small spheres from one or more materials in powder form. This type of processing will be referred to below by the generic term "spheronization". In the applications in the pharmaceutical field, these products comprise drugs or medicaments to which excipients are added; these products in powder form are to be amalgamated and then, with the aid of suitable binders, reduced to small spheres characterized by clearly determined physical and chemical properties, particularly in respect of the percentage of drug in the total mass of the individual sphere. In this type of processing, technical problems are encountered which are familiar to those skilled in the art. Particularly difficult problems are those connected with the dosage of the components and binders, with the dimensions of the spheres obtained at the end of processing and hence with the yield in dimensional terms, and with the contamination of the product and/or of the environment during processing.
Various processes of spheronization are currently employed, and possess a number of disadvantages. According to one of these known methods, the material or materials in powder form (for example, a drug and an excipient) are mixed and a liquid, for example water or a mixture of water and alcohol, is added thereto in order to form a moist composition which is then extruded. The extruded material is then placed in a spheronizer which possesses a plate rotating at a velocity of between 100 and 1000 revolutions per minute. The surface of the plate is fashioned to cause the deformation of the extruded material and the formation of the spheres. This method possesses the disadvantage that the material has to be mixed and amalgated with the liquid, then passed to the extruder, and the semi-processed extrudate has to be passed to the spheronizer. These transfers necessarily entail a loss of material and are responsible for contamination both of the material by the atmosphere and of the atmosphere by the material being processed. Furthermore, the spheronized material has to be removed from the spheronizer and placed in a suitable apparatus in order to be dried. This entails further losses of material and risks of contamination.
According to another known method, the spheres are produced in a fluidized bed within a suitable vessel into which is introduced, from the bottom, a gas having suitable physical and chemical properties. With this method, extensive losses of material are encountered owing to the friction between the particles being formed, with the production of powders which are highly contaminating.